US3271471A - Dimerization process - Google Patents

Dimerization process Download PDF

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Publication number
US3271471A
US3271471A US442151A US44215165A US3271471A US 3271471 A US3271471 A US 3271471A US 442151 A US442151 A US 442151A US 44215165 A US44215165 A US 44215165A US 3271471 A US3271471 A US 3271471A
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United States
Prior art keywords
xylylene
oxygen
diradical
stream
xylene
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Expired - Lifetime
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US442151A
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English (en)
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Leonard M Baker
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Union Carbide Corp
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Union Carbide Corp
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Publication date
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Priority to US442151A priority Critical patent/US3271471A/en
Priority to DE1593611A priority patent/DE1593611C3/de
Priority to FR54235A priority patent/FR1471813A/fr
Priority to BE678180D priority patent/BE678180A/xx
Priority to GB12504/66A priority patent/GB1147153A/en
Priority to NL6603807A priority patent/NL6603807A/xx
Application granted granted Critical
Publication of US3271471A publication Critical patent/US3271471A/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2603/00—Systems containing at least three condensed rings
    • C07C2603/92—Systems containing at least three condensed rings with a condensed ring system consisting of at least two mutually uncondensed aromatic ring systems, linked by an annular structure formed by carbon chains on non-adjacent positions of the aromatic system, e.g. cyclophanes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S585/00—Chemistry of hydrocarbon compounds
    • Y10S585/929—Special chemical considerations
    • Y10S585/942—Production of carbonium ion or hydrocarbon free-radical

Definitions

  • This method involves the pyrolytic polymerization of the cyclic dimer, di-p-xylylene.
  • this method comprises subliming dip-xylylene under vacuum at 100 C. to 300 C. to vaporize thecyclic dimer, pyrolyzing the vapors at 400 to 750 C. to form p-xylylene diradicals, the reactive monomeric species, and thereafter condensing and simultaneously polymerizing the p-xylylene diradicals to form p-xylylene polymers.
  • di-p-xylylene The synthesis of the starting material in the polymerization process, di-p-xylylene, is complicated due to its severely strained and sterically hindered structure.
  • the cyclic dimer was obtainable in only relatively small amounts.
  • Brown et al. Nature, 164, 915 (1949)
  • isolated di-p-xylylene as a by-product in the formation of poly-p-xylylene from p-xylene in trace amounts. It has also been prepared via a Wurtz reaction with 1,2-di-p-benzyl bromide ethane in only 2.1% yield as described by Cram ct al., I. Am. Chem. Soc., 93, 5691 (1951).
  • the present invention provides an improved process for the preparation of cyclic di-p-xylylene which comprises forming a vaporous stream of reactive p-xylylene diradicals having the formula by pyrolyzing a p-xylylene diradical precursor at temperatures from about 900 C. to about 1000 C. in an oxygen-enriched environment and contacting said stream in said environment with an iron base alloy composition consisting essentially of:
  • the reactive diradical, .p-xylene is generated in the process of the present invention by pyrolysis of a pxylylene diradical-precursor.
  • p-xylylene diradical-precursor is intended to define an organic aromatic composition which when subjected to pyrolytic conditions, i.e., temperatures between about 900 C. and 1000 C., will form p-xylylene diradicals either directly by thermal cleavage of a hydrogen radical (H-) or indirectly through disproportionation or other similar mechanisms.
  • p-xylylene diradical precursors are p-xylene, pseudocumene, cyclic tri-pxylylene, 1,2-di-p-tolylethane, diarylsulfones such as di-p-xylylsulfone, aryl bissulfones such as u,oc-bis(ethylsulfonyl)-p-xylene, and
  • compositions including derivatives of the above compositions containing ring and/or alpha substituents.
  • the pyrolytic reaction is conducted at a temperature of at least 900 C. and preferably from about 950 C.
  • Low partial pressures of the p-xylylene diradical-pre cursors are desirable in this process, preferably such that said reactant partial pressure is between about 0.1 and 20 mm. Hg, with optimum conditions generally being secured at a partial pressure of the p-xylylene diradical-precursor of about 1 to 10 mm. Hg.
  • an inert vaporous diluent in this process is not critical, it is often desirable for use in this process in order to reduce the partial pressure of the p-xylylene diradical-precursor and make it possible to operate at higher total pressures.
  • steam is a particularly desirable inert diluent in this process in that it permits operation at atmospheric pressure and has a protective effect in preventing decomposition of said diradical precursor, although there may also be employed other inert diluents as, for example, nitrogen, argon and like inert gases.
  • the total pressure of the system depends on the desired operating partial pressure of the precursor, and the amount of steam and/ or other diluents employed.
  • the pyrolysis reaction is preferably carried out at total pressures of l to 10 mm. Hg.
  • the amount of steam present in this process is not narrowly critical but when employed it is preferably present in an amount of at least about 50 moles per mole of said precursor and generally between about 50 to 300 moles per mole of said precursor although between about to about 200 moles per mole of precursor are most preferred. Excess steam however is not detrimental to the process.
  • Pyrolysis of the p-xylylene diradical-precursor is conveniently conducted by vaporizing the precursor and passing it through a high temperature thermal cracking reactor for a short period of time.
  • Time of contact in the reaction chamber must be at least sufficient to pyrolyzed or crack a portion of the precursor into the reactive diradical, p-xylylene, but not so long that charring or complete decomposition occurs.
  • Contact time depends to a great degree on the particular temperature selected for pyrolysis; the lower the temperature the longer the permissible contact time and vice versa. At most desirable 3 conditions of about 975 C. contact times are preferably between about 0.03 to 0.06 second. Seldom would it be desirable to have a contact time greater than 0.1 second. At the higher operating temperatures, contact times of 0.03, second or shorter may at times be indicated.
  • Condensation of the p-xy'lylene diradicals into the di-pxylylene is accomplished in the presence of an organic solvent.
  • an organic solvent In order to stabilize the composition of the pyrolysate vapors and prevent disproportionation of diradical and initial reactant back to monoradical it is preferable to cool to about 500 C. but not below about 400 C. in order to avoid dropping below the condensation temperature of the reactive diradical before it is absorbed in the organic solvent. Cooling to below the ceiling condensation temperature in the absence of the organic solvent causes almost spontaneous polymerization of the reactive diradical to a p-xylylene polymer. This ceiling condensation temperature is generally below about 400 C. depending somewhat on the operating pressure. However, in the vaporous state, the reactive diradical is relatively stable and does not polymerize.
  • the cooling of the pyrolysate vapors may be accomplished in any of several convenient means.
  • internal or external condensers, cooling coils, tubes or the like can be employed immediately after the pyrolysis zone, or if desired, natural cooling caused by long runs of air cooled tubing or piping from the pyrolysis zone to the condensing medium can be used.
  • direct cooling means e.g., injection of a cool inert vapor into the pyrolysate vapors, are employed in order to rapidly reduces the reaction temperature thereby avoiding undesired shifts in stream composition.
  • the di-p-xylylene product forms on the condensation of the vaporous diradicals in the presence of the fluid medium. It is not essential however that the fluid medium be in the liquid state. While this is not desirable, the condensation can be accomplished equally as well by mixing the pyrolysate vapors with vaporous aromatic solvent and simultaneously condensing the total mixture to the liquid state for recovery of the product.
  • Suitable gas scrubbers or spray tanks can be used to remove and condense the p-xylylene diradicals into the di-p-xylylene in this process.
  • Gas scrubbing devices are particularly desirable in continuous operation, and with the use of such very high boiling organic solvents as mineral oil where the di-p-xylylene can be recovered by distillation from the solvent.
  • the cooled pyrolysate vapors of the reactive diradical are collected in a liquid medium, merely bubbling or dispersing the vapors below the liquid level of the aromatic solvent is also adequate to cause the p-xylylene to dimerize to the di-p-xylylene and be recovered from the solvent solution.
  • the bath into which these vapors are condensed can be maintained at any temperature below about 300 C., and preferably from 100 to 250 C.
  • the term fluid media is intended to cover both the liquid or gaseous state of the solvent medium in which the pyrolysate vapors are collected.
  • An environment comprised of the alloy composition can be attained through use of a packing comprised of said alloy in a high temperature reactor.
  • the alloy can take the form of a steel wool or woven mesh packing or any other suitable form which provides a high surface area to volume ratio.
  • the alloy can also be present as the material used in the construction of the reaction chamber or as a liner in the reac tion chamber although any means or form for providing an environment wherein the formation of the reactive active diradicals were formed in contact with the oxygenated packing and thereafter passed to a subsequent quenching zone wherein the diradicals were condensed in a fluid medium containing an inert organic solvent, in this instance, p-xylene, maintained at temperatures below about 300 C. to form di-p-xylylene.
  • Oxygen in amounts of from about 0.05 to about 0.15 mole of oxygen per mole of p-xy'lylene diradical-precursor continually fed to the pyrolysis feed stream is considered critical in obtaining the increased yields and efiicien-cies described hereinabove.
  • Oxygen in molar proportions less than about 0.05 mole oxygen per mole of precursor was found to have no appreciable efiect on either yield or efl'lciency.
  • Oxygen was fed to the pyrolysis stream in molar ratios varying from 0.05/1 to 0.40/1 moles oxygen per mole p-xylene.
  • the oxygen-enriched pyrolysis stream was fed to the packed reactor so that the stream contacted the packing upon its passage through the reactor.
  • the re- 1 While not wishing to be bound by any theory or proposed mechanism, it is believed that the yields and overall efficiency of the process are increased by the present invention by minimizing the harmful side reaction of demethylation and removing the free hydrogen radicals produced in the pyrolysis by rendering them innocuous through conversion to steam in situ.
  • a p-xylyl monoradical. and a hydrogen radical are initially formed:
  • the hydrogen radical can react with p-xylene to cause demethylation:
  • the quantity of oxygen feed to the reaction stream substantially corresponds to stoichiometric proportions relative to the hydrogen radicals produced.
  • the addition of substantially stoichiometric proportions of oxygen has a decidedly beneficial effect in a pyrolysis carried out over a packing or in a zone comprised of the iron base alloy composition defined hereinabove, whereas under identical conditions in the absence of the metal surface, there is no benefit.
  • pxylene and steam are fed to an atmospheric pressure reactor packed with a mesh of the alloy composition above defined.
  • Oxygen in molar ratios of from about 0.05 to 0.15 mole oxygen per mole p-xylene and more preferably 0.05 to 0.10 mole oxygen per mole p-xylene, is fed to the pyrolysis stream most conveniently in the form of an air bleed.
  • the temperature in the reactor is -maintained between about 900C. to 1000 C. and most preferably in the range of about 950 C. to about 975 C.
  • the p-xylene and steam flow rates are adjusted so as to give a contact time of about 0.03 to 0.6 second and a p-xylene partial pressure of 1.0 to 10 mm. Hg.
  • the pyrolysate vapors are cooled at the outlet of the pyrolysis zone to a temperature of about 400-700 C. and then passed into a quenching bath of boiling organic solvent where the condensation of the diradical to the cyclic dimer takes place.
  • the remaining uncondensed vapors are subsequently condensed.
  • the aqueous layer is decanted.
  • the condensed p-xylene is recycled.
  • the solution containing the dimer is concentrated by flashing or reduced pressure distillation to about one-tenth its original volume.
  • On cooling the di-p-xylylene crystallizes from the p-xylene solution in high purity and is separated from the mother liqnor by filtration or by centrifugation, washed and dried.
  • dimer recovery proc ess can be conducted either batch-wise or continuously.
  • the use of p-xylene as the condensation medium is highly desirable in the continuous system inasmuch as it can be recycled within the system serving not only as the reactant but also as the condensation medium and problems of handling a separate solvent are avoided.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US442151A 1965-03-23 1965-03-23 Dimerization process Expired - Lifetime US3271471A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
US442151A US3271471A (en) 1965-03-23 1965-03-23 Dimerization process
DE1593611A DE1593611C3 (de) 1965-03-23 1966-03-19 Verfahren zur Herstellung von cyclischem Di-p-xylylen durch Pyrolyse von p-Xylol bei 900 bis 1000 Grad C
FR54235A FR1471813A (fr) 1965-03-23 1966-03-21 Procédé perfectionné de dimérisation
BE678180D BE678180A (enrdf_load_stackoverflow) 1965-03-23 1966-03-21
GB12504/66A GB1147153A (en) 1965-03-23 1966-03-22 Production of cyclic di-p-xylylene
NL6603807A NL6603807A (enrdf_load_stackoverflow) 1965-03-23 1966-03-23

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US442151A US3271471A (en) 1965-03-23 1965-03-23 Dimerization process

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US3271471A true US3271471A (en) 1966-09-06

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BE (1) BE678180A (enrdf_load_stackoverflow)
DE (1) DE1593611C3 (enrdf_load_stackoverflow)
GB (1) GB1147153A (enrdf_load_stackoverflow)
NL (1) NL6603807A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3440295A (en) * 1966-12-27 1969-04-22 Union Carbide Corp Para-xylene preparation using hydrogen scavenger
US4532369A (en) * 1982-10-30 1985-07-30 Merck Patent Gesellschaft Mit Beschrankter Haftung Process for the preparation of [2,2]-paracyclophane
US5288504A (en) * 1988-09-09 1994-02-22 The Ronald T. Dodge Company Pharmaceuticals microencapsulated by vapor deposited polymers and method
JP2015529205A (ja) * 2012-08-30 2015-10-05 カーバー サイエンティフィック インコーポレイテッドＣａｒｖｅｒ Ｓｃｉｅｎｔｉｆｉｃ， Ｉｎｃ． ［２，２］パラシクロファンおよび関連化合物の形成ならびにシクロファンからのポリマーの形成方法
US10227432B2 (en) 2011-08-31 2019-03-12 Carver Scientific, Inc. Formation of xylylene type copolymers, block polymers, and mixed composition materials

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118420428B (zh) * 2024-04-30 2025-02-18 深圳方寸达科技有限公司 一种n型派瑞林单体的光化学制备方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2719131A (en) * 1953-05-15 1955-09-27 Du Pont Production of p-xylene polymers
US3149175A (en) * 1960-08-22 1964-09-15 Union Carbide Corp Preparation of di-para-xylylenes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2719131A (en) * 1953-05-15 1955-09-27 Du Pont Production of p-xylene polymers
US3149175A (en) * 1960-08-22 1964-09-15 Union Carbide Corp Preparation of di-para-xylylenes

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3440295A (en) * 1966-12-27 1969-04-22 Union Carbide Corp Para-xylene preparation using hydrogen scavenger
US4532369A (en) * 1982-10-30 1985-07-30 Merck Patent Gesellschaft Mit Beschrankter Haftung Process for the preparation of [2,2]-paracyclophane
US5288504A (en) * 1988-09-09 1994-02-22 The Ronald T. Dodge Company Pharmaceuticals microencapsulated by vapor deposited polymers and method
US5393533A (en) * 1988-09-09 1995-02-28 The Ronald T. Dodge Company Pharmaceuticals microencapsulated by vapor deposited polymers and method
US10227432B2 (en) 2011-08-31 2019-03-12 Carver Scientific, Inc. Formation of xylylene type copolymers, block polymers, and mixed composition materials
JP2015529205A (ja) * 2012-08-30 2015-10-05 カーバー サイエンティフィック インコーポレイテッドＣａｒｖｅｒ Ｓｃｉｅｎｔｉｆｉｃ， Ｉｎｃ． ［２，２］パラシクロファンおよび関連化合物の形成ならびにシクロファンからのポリマーの形成方法
EP2890665A4 (en) * 2012-08-30 2016-05-25 Carver Scient Inc FORMATION OF [2,2] PARACYCLOPHANE AND RELATED COMPOUNDS AND METHOD FOR THE PREPARATION OF POLYMERS FROM CYCLOPHANESE
AU2012388717B2 (en) * 2012-08-30 2017-03-09 Carver Scientific, Inc. Formation of [2,2] paracyclophane and related compounds and methods for the formation of polymers from cyclophanes

Also Published As

Publication number Publication date
GB1147153A (en) 1969-04-02
BE678180A (enrdf_load_stackoverflow) 1966-09-21
DE1593611B2 (de) 1974-11-28
DE1593611A1 (de) 1970-08-06
NL6603807A (enrdf_load_stackoverflow) 1966-09-26
DE1593611C3 (de) 1975-07-10

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